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Oriental Blue and White, particularly those made in China, has had during the whole period of its development a unique quality which has never been approached in any other blue and white porcelain. The reasons for this can be appreciated ... read on

Pottery had been produced in China since neolithic times. Until T’ang Dynasty (AD618-906), plain- glazed high-fired porcelain was produced. During Sung Dynasty (960-1279) encountered a delayed trend of the arrival of porcelain age. There was limited appeal over for porcelain characteristics - a marble-like whiteness and a clear brilliant finish throughout the Sung Dynasty. However, a bluish-white porcelain known as Ching Pai was produced in the Kiangsi Province. During Mongol Yuan Dynasty (after Sung Dynasty) the only porcelain made for the Court, shu-fu or “privy council” were variations of Ching Pai decorated with brown iron spots, copper red and cobalt blue floral patterns under the glaze.

MATERIALS USED
The underglazed blue decoration, proved to be the most successful and popular when a transparent and colorless glaze replaced chingpai which freed from all impurities to appear milky white. A fine blue and white was thus produced at Ching-te Chen and Fukien province (called the “porcelain capital”)

Ching-te Chen located by the mountains of Kangsi and watered by two rivers to form an excellent port. The wealth of the city was derived solely from the manufacture of porcelain with 3000 kilns were kept burning throughout the year. The city was clearly a major industrial centre for well ordered and well supplied with raw materials the potters needed.

The most important materials were the two clays used in the manufactured of porcelain, kaolin and petuntse which comes from the Kangsi mountains. Kaolin is a decomposed clay that fuses at a temperature of about 1,740 degrees centrigrade, which is too high for practical purposes and petuntse is less decomposed and fuses at rather a lower temperature. Both are essential to the preparation of porcelain paste, when mixed together forms the finest porcelain. The Chinese called kaolin the ‘bones’ of the porcelain and the petuntse the ‘flesh’.

THE MAKING
Once the clay had been found, they were ground to form soft white bricks and mixed with certain mineral salts and water. Quartz and crystalline sand were heated and pulverised and added to the mixture which to be put aside for several years to mature to form a porcelain paste. The paste was then beaten, kneaded to remove air bubbles that might expand in the heat of the kiln.

Modeling of shapes as wished were moulded into perfect shape, trimmed with chisel to give correct thinness. For large jar or vase, it is divided into 2 -3 sections which were then luted together with slip (mixture of clay and water to from a consistency cream) to ensure the join is smooth. The objects were left to dry up to a year before the potters sort them out into various categories for attachment of handles and spouts.

DECORATION
The wares were now ready to be decorated with cobalt blue. It a huge difficult task liken to writing ink on blotting paper with a full pen. If the artist hesitate with his brush, result is a smudge and if he moves it too quickly, there is no result at all. Hence, great skill was needed on part of the decorator. More difficulties were encountered in grinding of the imported cobalts often leave particles of poorly ground pigment in the mixture.

When the brush is too heavily loaded, they caused blotchy effect - “heaped and piled”. Particles of cobalt from the bristles of the brush would sometimes caused bursting of minute rust spots through the glaze. The potters later found other methods to grind their local cobalt for an even application in the fifteen century making them able to etch the outline of the motif first the filled it in with paler walsh.

There were strong evidence to suggest that during the Yuan Dynasty and the early period of Ming, the cobalt was imported from the Middle East known as hui hui ching or ‘Mohammedan Blue which has always been greatly admired. A similar variety of cobalt ~ su-ma-li or su-ni-po also reached China between 1426 -1448 imported from Sumatra and Zanzibar.

By the beginning of Cheng-hua reign, the supplies of imported cobalt ran out and the Chinese revert to native resources. The native resources contained manganese cause the ware to turn greyish blue. A better resource was found in the 16th century and enable the potters to decorate their wares again to the rich dark blue. By the end of the century it was then exhausted. For early Kang-hsi, potters were able to purify inferior cobalt that have delighted generations of connoisseurs ever since. After the main decoration, the reign mark or nien ho was added in cobalt blue to the base of the piece in question, during the Hsuan te period. The wares were now ready to be glazed. The glaze was composed of petuntse mixed with water, fern ash and lime to give it depth and brilliance. Before firing it was opaque concealing the decoration but became transparent when kiln. The glaze was either blown. on the body through a bamboo pipe or the vessel was dipped into a pot of glaze and swilled around. It was then held up to allow any excess glaze to run off. We can see marks made by the potter’s fingers as he gripped the vessel.

FIRING OF THE WARES
After being glazed, the wares are taken to the kilns to be fired. The kilns were built of brick between 12 and 20ft high and as 50ft long. Kilns often tended to disintegrate after several firings and have to rebuilt. The wares are then place in saggars (strong cylindrical vessels made of fire clay) to protect from falling ash in the kiln. The firing would take at least 36 hours or longer. The maximum recorded was 19 days. The saggars were allowed to cool off for another day before being open.

Not until the kilns were opened, the potters have no idea of their successful task, of which often was a total loss. In order to produce a good blue, it is necessary to remove all the oxygen in the kiln, so that the cobalt oxide can be converted into a blue cobalt silicate. When the kiln is open prematurely, the cobalt silicate is reconverted to cobalt oxide which burns black in the heat of the kiln. Many of the 14th century and later provincial wares show decoration of grey or even blackish tone.

Until the Cheng-hua period, when 2 coats of glaze were frequently applied over the decoration to try to avoid the hazard. During the 16th and 17th century the finer examples of blue and white were always fired in strong reducing atmosphere to reduce the reconversion but ended with too much of wood smoke. This hazard was avoided in the 18th and 19th century as it was ruled that kilns were never opened until they had completely cooled down.

IMPERIAL WARES
The Chinese discovered most of the firing of porcelain were by trial and error and the hazards in the kiln throughout the 14th and 15th century were very considerable. In fact no one knew for how certain how even the finest wares intended for the court would turn out until the kiln were opened. This almost accounts for the number of finely ported and decorated wares of the Ming dynasty available today with some blemish which were consign for 'commercial' category rather than allowing them be considered of imperial quality.

Yuan Dynasty 1279-1368 AD
Bowl with carved panels undeglazed
Blue Leaves and Red Flowers

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